Test for cations

Magnesium chloride is given a flame test what colour flame will you see?

Two salts have been accidentally mixed together. They contain potassium cations and copper cations. What colours will the flame show?

• Green and lilac

• Lilac and red

• Green and brick red

• Lilac and orange

• Green and Orange

A solution containing Iron(II) cations forms what colour precipitate when sodium hydroxide is added.

Some sodium hydroxide solution is accidentally spilt onto to some copper(II)sulphate solution. What would you expect to see?

• The copper(II)sulphate solution goes from blue to colourless

• A blue precipitate forms

• A green precipitate forms

• No change

A pupil suspects an unknown salt contains ammonium NH₄⁺ ions. They place some red litmus paper at the top of a test tube to test for ammonia gas but see no change. What steps did they forget for the test?

• Add some sodium hydroxide solution

• Heat the tube gently

• Putting the red litmus paper into the solid

• Nothing, the unknown salt must not have ammonium ions

An unknown salt produces an orange/yellow flame. What cation does it contain?

• sodium

• lithium

• potassium

• calcium

• copper

After adding sodium hydroxide to an unknown solution a reddish-brown precipitate is formed. The solution contains which cation?

• Fe(II)

• Fe(III)

• Fe(V)

• Cu(II)

An unknown salt produces a red flame during in a flame test. What cation does it contain?

• chloride

• lithium

• copper

• calcium

Which of the following elements will form a cation?

• Arsenic

• Copper

• Bromine

• Fluorine

NaOH is added to an unknown solution. A blue ppt forms. The formula of the ion is:

• Fe
• Fe3+
• Fe2+
• Cu2+